While somewhat controversial, ketogenic diets have gone mainstream in 2018 thanks to celebrity endorsements, including from Kim Kardashian.

While for the past three decades, they have often been used for weight loss, ketogenic diets first appeared in the 1920s as a treatment for epilepsy. You’ll find very little contention about using ketogenic diets here: Research shows they can be powerfully effective, especially when medications don’t work for epilepsy.

In the 1960s, some health care professionals began using ketogenic diets for obesity, though they fell in and out of favor as other diet plans—such as low-fat or calorie-restricted diets—became more popular (thanks to misleading food industry marketing).

Today, you’ll see ketogenic diets promoted to prevent disease, increase energy, boost physical and mental performance, and so much more. But let’s face it: Most people want to try keto to lose weight. While that’s not a bad thing—you can lose weight doing it—ketogenic diets were never designed for weight loss, and done incorrectly, a side effect can actually make you gain weight.

What is the ketogenic diet?

Simply put, a ketogenic diet is very high in fat, moderate in protein, and very low in carbohydrates. The idea behind keto is to keep your fat-accumulating hormone, insulin, low by keeping your blood sugar low. In doing so, you turn on fat-burning genes while suppressing the abdominal-fat-amassing machinery.

While actual percentages vary a little, traditionally ketogenic diets reduce carbohydrates to less than 50 grams a day. That’s pretty low: Something like an apple and a cup of quinoa would easily clock in at about 50 grams.

Especially with animal fats, you want to choose the very highest quality. Toxins congregate in fatty tissue, so when you eat, say, a fatty grain-fed steak from a factory-farmed cow, you’re ingesting those toxins.

You'll balance those healthy fats out with loads of gut-healing, microbiome-supporting, low-carbohydrate plant-based foods, including leafy and cruciferous vegetables.

These dietary restrictions work for some people. However, can you picture yourself passing on bread and desserts forever? Does this sound like the kind of plan you could more or less stick with for life? If not, a ketogenic diet might not be for you. And it doesn’t have to be.

What foods should you avoid on the ketogenic diet?

You will not be having your cake or eating it…or for that matter, pretty much any packaged, processed, or higher-carbohydrate foods, even healthier ones like higher-sugar fruits and legumes.

When you restrict your carbohydrate intake to less than 50 grams daily, you can still fit in plenty of nonstarchy vegetables, maybe some low-glycemic (meaning they don’t bump your blood sugar) blueberries and other berries, and a small amount of non-gluten grains like quinoa (actually a seed and complete protein). But you’ve got very little wiggle room there before you theoretically get knocked out of ketosis.

You also want to restrict protein intake since some amino acids like glycine and arginine are glucogenic (convert to glucose) and could inhibit ketosis. Personally, I think this is overblown, and you can allow some protein into a ketogenic plan. Most foods high in dietary fat, like steak or fish and even nuts, will contain some protein.

How is keto different from the Atkins diet?

Perhaps the first person to really put ketogenic diets on the map was Dr. Robert C. Atkins, a cantankerous medical doctor who began experimenting with a low-carb diet in 1963. His first book, Dr. Atkins Diet Revolution, was published in 1972. Dr. Atkins died in 2003 from a tragic fall (interestingly, the Atkins website’s timeline does not mention his death), but his diet plan lives on today.

Dr. Atkins talked a lot about ketosis back then, and the original Atkins diet was a far cry from what you see today; it was pretty hard-core. Save for lettuce, you consumed zero carbs, and even during maintenance, you kept your carb intake below 40 grams daily.

That plan didn’t allow much variety or leeway. Eggs, two small green salads a day, gelatin for dessert, cheese (up to 4 ounces daily), bone broth, no-calorie liquids, and lots of meat: That was pretty much it for the first week. After level one, you added vegetables like broccoli. Yes, you would be in ketosis doing the original Atkins diet, but for most people, that spartan plan would get boring quickly.

Perhaps noticing his patients’ boredom, Atkins in subsequent versions of the Atkins diet shifted the focus from ketosis to what are called "net carbs," or your final carbohydrate count after you subtract fiber and sugar alcohols.

The Atkins diet today hardly resembles the original 1972 plan. You’ve got two options. With Atkins 20®, you start with 20 grams of net carbs a day. During the first two weeks on that plan, most of your carbs come from vegetables like leafy greens. You can also have high-fat dairy like cream, sour cream, and most hard cheeses.

The second plan (Atkins 40®) is a bit more lenient: You start with 40 grams of net carbs a day. About one-third of those carbohydrates should come from vegetables, with the remaining amount coming from fruit, nuts, and/or whole grains. To fit those foods within your 40-gram carb allotment, you’ll need serious portion control.

Both plans also include three servings of protein (each 4 to 6 ounces) and three servings of dietary fat, including foods like butter, salad dressings, and olive oil. Once you’re past the induction phase, you start adding 5 to 10 grams of carbohydrate at a time until you find your carb threshold.

The shift from ketosis (hardly mentioned today on the Atkins diet) to net carbs allowed more vegetables and other plant-based carbohydrates into the plan (good) but also opened the floodgates for low-carb processed junk foods (not good). Of note, when you subtract fiber content, most green vegetables contain very few carbohydrates.

Today, you can buy a huge array of Atkins shakes, snacks, meal replacement bars, frozen entrees, and even weekly or monthly meal-delivery kits on their website. They offer low-carb versions of comfort foods like Chocolate Peanut Candies, Mac and Cheese, a Stone-Fired Pepperoni Pizza, and Meat Lasagna.

Many of these snacks contain poor-quality ingredients, including artificial colors and sucralose, an artificial sweetener that studies show adversely affects your gut microbiome, increasing insulin resistance. Other options, including their frozen entrees, contain the top food sensitivities many people have issues with, like gluten, dairy, soy, eggs, and peanuts as well as junk oils, like soybean oil.

Simply put, among this wide array of processed foods are included lots of low-carb junk foods—bad news for your gut and overall health. Besides increasing inflammation, they can trigger leaky gut, insulin resistance, and other issues that will eventually stall your fat loss as they sabotage your health.

In all fairness, you can do these plans without eating all those processed foods, although (let’s face it!) convenience and cravings mean you’ll likely be tempted to try them. And they tap into that weakness for "cheating" by making these options easily available. Who would refuse comfort food that is "compliant" with a diet? You can have your cake and eat it too, literally. I call this pseudo-dieting. Even then, eating potentially reactive foods like dairy (which is allowed from the very beginning on Atkins) can either aggravate or trigger food sensitivities ("no bueno").

Mistakes people make on the keto diet.

Tapping into consumers’ desire to glean the benefits of ketosis right this minute—or in the next 30 minutes—manufacturers have created powders and other supplements that promise you can enjoy your favorite foods and still get into ketosis. These supplements—called exogenous ketones—aren’t necessarily bad, but neither are they a free pass to indulge and then effortlessly shift into ketosis.

Then you’ve got "keto-approved" junk foods like cookies, candy, and bread that promise to keep you in ketosis even as you indulge in your favorite comfort foods. The flip side is ketogenic diets that include almost no plant foods, focusing instead on meat, meat, and more meat. Bring on the bacon. Slather your steak in butter. Who needs vegetables? (Hint: You do!) Ketogenic diets are a practical invitation for vegetable-phobic people, and when you skip out on gut-healing plant foods, you create microbiome mayhem.

Ultimately, poorly designed ketogenic plans become hyper-fixated on a single issue, like counting carbs or getting enough fat. Doing that neglects other highly important factors, like nutrient density and eating whole, unprocessed foods that will have a positive impact on gut and overall health.

How does the keto diet affect your hormones?

As you eliminate blood-sugar-elevating carbohydrates, you stabilize blood sugar levels and lower insulin levels, subsequently benefiting other hormones. At least theoretically that should happen.

Unfortunately, that path isn’t so clear-cut and will differ among individuals. The transition to a ketogenic diet might also differently affect hormones than maintaining the plan long-term. Hormones are complicated, and other factors beyond diet—including sleep quality, stress levels, circadian rhythm nutrient status, and your overall health—dramatically affect whether they become balanced or unbalanced.

Take your stress hormone cortisol: It stays highest in the morning and gradually tapers throughout the day. Measuring cortisol in the morning might yield an entirely different result from testing in the evening. Researchers speculate ketogenic diets might raise this stress hormone, but many other factors also come into play here that may have nothing to do with your diet.

Research about ketogenic diets and hormonal balances can become complicated and inconclusive. While it feels tempting to say any well-designed diet plan can optimize hormonal levels, the truth isn’t always so linear or clear-cut. Take these three hormones:

1. How the keto diet affects insulin.

Research here is conflicting. While you might think reducing insulin-triggering carbohydrate foods would improve insulin sensitivity, that isn’t always the case. Rodent studies found at least in the short-term, ketogenic diets increased glucose intolerance and insulin resistance. Researchers speculate part of this insulin resistance occurs because of keto-adaptation, and once your body adjusts to ketosis, you become more insulin sensitive. Your mileage will vary, of course, and I believe going too low-carb could create these and other potential dangers.

2. How the keto diet affects ghrelin.

Many dieters complain that hunger sabotages their success. Ghrelin is your hunger hormone that tells you to eat. Research shows ketogenic diets suppress ghrelin, keeping you fuller longer. That makes sense: When you’re eating sufficient dietary fat and calories, you’re unlikely to be hungry.

3. How the keto diet affects growth hormone.

If you lift weights on a ketogenic diet, you might fear losing muscle mass taking in lower amounts of protein. That doesn’t seem to be the case since your body preferentially utilizes fat rather than protein during ketosis. Growth hormone, an anabolic hormone sometimes called your fountain-of-youth hormone because it keeps you lean and toned, plays a major role in regulating muscle growth and development, stimulating muscle protein synthesis. Researchers find a very-low carbohydrate diet with sufficient protein does not affect growth hormone levels, at least in the short-term. If you’re a regular lifter, you might want to consider slightly increasing your protein intake during workout days and supplementing with a branched-chain amino acid (BCAA) supplement. Cyclical keto, where you would eat a higher-carbohydrate diet during your workout days, also makes for a smart strategy to maintain muscle.

What really matters here is how you feel when eating a particular way. Your mood, energy levels, lab results, and mental sharpness (to name a few) are powerful indicators of whether a diet works for you both short- and long-term. Body awareness is key as well as not following a specific diet because you think it’s the "right" diet to follow. Listen to your body. And most importantly, if you feel off, seek the help of a functional medicine practitioner to assist you in uncovering the root cause of your malaise or diet resistance. Sometimes all it takes is a few small tweaks to improve your health.

Does the keto diet make sense for everyone?

Just because your favorite celebrity endorses a program doesn’t mean you should try it. No plan works for everyone, and that goes double for ketogenic diets. As I mentioned before, while they can initially create fat loss, ketogenic diets were never designed to help you lose weight. Especially if you’re eating too many calories—very possible on a high-fat ketogenic diet—you can be in ketosis and not lose weight (or even gain weight). Likewise, many people lose weight just fine without ever "going keto."

If you’re considering a ketogenic diet for other reasons—such as to prevent disease risk or to have more energy and boost your brain power—I strongly suggest reading what I have to say next about the pros and cons of doing this plan and asking yourself these questions:

What are your short-term and long-term goals?

Can you realistically cut out healthier higher-carbohydrate foods (sometimes including berries and other fruit, legumes, and non-gluten grains) for a period of time?

Are you prepared to work through "keto flu" and other potential drawbacks as your body shifts from glucose to fat (ketones) as its dominant fuel source?

Can your body handle higher amounts of dietary fat? (To make this process easier, I recommend my patients gradually increase their fat intake. Your digestive enzymes need time to ramp up to be able to handle the higher fat content in your digestive tract, or it can cause unpleasant gas, bloating, and diarrhea.) Remember: If the thought of eating higher-fat foods like steak or avocado doesn’t appeal to you, keto probably isn't for you.

Can you handle potential social restrictions on this plan, such as not being able to partake in certain foods or drinks (alcohol) your friends enjoy?

Can you realistically stick with a high-fat ketogenic diet long-term?

Yes, you can do a ketogenic diet in a healthy way, but doing so demands dedication, planning, and knowing exactly how to do it correctly. Too often, I see patients get keto wrong…with potentially disastrous results.

What are the pros of the ketogenic diet?

1. The keto diet is satiating.

Eating healthy fats and moderate protein keeps you satiated, meaning you eat less overall. This also allows for a variety of satisfying foods. One drawback of many diets is that people get hungry and succumb to their favorite "forbidden" foods. That’s less likely to happen on a ketogenic diet.

2. The keto diet is anti-inflammatory.

3. The keto diet is gut-healing.

Combined with plenty of plant foods, keto done the right way is a great way to heal your gut.

4. The keto diet can improve energy and clarity.

After the transition to utilizing ketones for fuel, many people report feeling better, having more energy, and experience improved mental clarity.

5. The keto diet can help you lose weight.

You will probably lose weight on the plan and get other health benefits.

These are the cons of doing the keto diet:

1. The keto diet is limiting.

If you need a lot of variety in your meal plans, keto might leave you feeling limited and bored.

2. The keto diet can contain too much fat for some.

Some people don’t do well eating the high amounts of dietary fat a ketogenic diet requires. Researchers debate whether humans are designed to digest these high amounts of fat.

3. The keto diet can be a social bummer.

Sticking with the plan might be challenging during vacations, social engagements, and other times keto-approved foods aren’t available.

4. The keto diet can result in the keto "flu."

Even if you take the right precautions like optimizing electrolytes, keto flu as you transition into utilizing ketones for fuel can be intense enough to turn some people off keto diets.

5. The keto diet can get in the way of long-term weight loss.

If you’re using ketosis for weight loss, you may see initial results, but eating too many calories from any food can stall fat loss or make you gain weight.

How to go keto.

Well aware of potential limitations, like keto flu (discussed below) and the compromises you have to make on a restrictive eating plan, you’re ready to give keto a try. I’ve talked about the wrong way to do it, but how can you intelligently get into ketosis and get all of its benefits, including promoting great gut health?

1. Eat low-glycemic plant foods.

You can still eat plenty of healthy dietary fats and also include gut-healing foods like leafy and cruciferous greens, prebiotic-rich foods like garlic and dandelion greens, and probiotic rock stars including kimchi and unpasteurized sauerkraut. Even with a daily 50-gram carb allowance, you can find a lot of anti-inflammatory, gut-supporting foods.

2. Optimize electrolytes.

Electrolyte imbalances become a chief culprit with keto flu. Focus on mineral-rich foods, including avocado, nuts, seeds, and leafy greens to get magnesium, potassium, and other minerals. You might also consider a no-sugar-added electrolyte supplement formula. And sprinkle Himalayan sea salt onto your food.

4. Remember that calories count.

Eating a 5,000-calorie diet high in fat will certainly put you in ketosis, but you probably won’t lose weight because those excessive calories have to go somewhere. You needn’t be as adamant about calories doing a ketogenic diet, but they do still matter. Drizzling 500 calories of MCT oil or butter onto your steak will probably get you into ketosis, but the scales aren’t going to provide you much love. However, having the right amount of extra fat in the diet while keeping starchy carbohydrates low will make you into a fat-burning machine.

5. Ketosis is a tool, not a way of life.

Feel free to practice cyclical ketosis (maybe doing a ketogenic diet five days a week and going higher in healthy carbs the other two days) or whatever works for you. I’ve never heard an expert say you should be in ketosis 24/7, and militantly sticking with this plan can ultimately stall your goals. Once you’re in a state of ketosis, you can transition to a more flexible ketogenic plan. You can rotate complex carbs, like sweet potatoes, pumpkin, and butternut squash, into the diet every three to four days to maintain your glycogen stores if you work out and lift weights regularly.

How do you know if you're in a state of ketosis?

Some people just "know" they are in ketosis. For others, they want more concrete proof. Signs you’re in ketosis include weight loss, a euphoric feeling that improves thinking and cognition, more energy, mental sharpness, and even moods, with fewer spikes and crashes in your blood sugar levels that lead to mood swings, lethargy, and other issues.

You’ve got to earn those benefits. They usually occur only once you're keto-adapted, which might take days or weeks. In the interim, you might experience bad breath and the keto flu (more on that in a second), which are less-than-pleasant, though usually temporary.

If you absolutely want to know how your body is utilizing ketones, you have three ways to do so:

1. A ketone meter.

2. Ketone strips.

If pricking your finger regularly isn't for you, you can also use ketone strips, which measure ketones in your urine. Some critics argue they aren’t as accurate as checking blood levels, but they can provide some indication of whether you’re in ketosis, they’re less expensive than glucose meters, and you don't have to prick your finger multiple times daily.

3. Breath analyzer.

This device measures the amount of acetone (another ketone) you release in your breath when you are in ketosis. (Acetone is also the ketone responsible for bad breath when you’re in ketosis.) There are a number of kits on the market. One study showed they are as effective as ketone strips for testing ketone levels, but critics argue both have drawbacks including testing for only one specific ketone.

What is keto flu (and how do you avoid it)?

You’re now gung-ho on ketosis, ready to get started, and you jump right in full-on. Within the first few days, you start feeling worse than you have felt in a long time.

Headaches, fatigue, brain fog, nausea, bad sleep, and a propensity to want to lie on the couch and watch Netflix marathons rather than hit the gym: not a recipe for a fun weekend, huh? Wait a second; you thought ketosis was the answer to your problems, and now it’s created new ones?

Those are some of the signs of keto "flu." You’re snappy at your co-workers, your sleep becomes terrible, and you might even feel lightheaded.

Unpleasant as these sound—and they are—rest assured, these symptoms pass: sometimes in a few days, other times longer. But while they occur, they can suck.

For some people, keto flu hits hard and makes the first few days of a ketogenic diet practically unbearable. Others breeze through it as their mitochondria transition into utilizing ketones as fuel.

As your body adapts, hormonal fluctuations can create keto flu; so can electrolyte imbalances. I strongly recommend replenishing sodium and other minerals you’re losing, along with water weight, with a sugar-free (not artificially sweetened) electrolyte solution or trace minerals during the first few days on a ketogenic diet.

Here are a few ways to restore nutrient levels and minimize the symptoms of keto flu:

Look for a no-sugar-added, professionally designed electrolyte formula.

Sip mineral-rich bone broth.

Eat plenty of nutrient-rich foods like avocado, nuts, seeds, and vegetables, which can also help replenish those nutrient levels.

If you’re doing those things and keto flu still hijacks your overall well-being, slightly increase your carbohydrate intake. As I’ve mentioned, some people can handle more nutrient-dense carbohydrates and still remain in ketosis. The point is to be flexible, not dogmatic. If you’re miserable, let your body ease into ketosis more slowly.

The new ketogenic diet: How to do keto in a healthy way.

While a ketogenic diet (or the Atkins diet done intelligently) can be healthy and create results, too many people make mistakes that can derail their long-term progress on these plans. In my practice, where I work with patients on gut-healing (you can get my free kickstart guide to gut-healing here), I’ve found these seven strategies will help you design and maintain a healthier ketogenic diet plan:

1. It's all in the balance.

Dousing your steak with butter, swigging MCT oil out of the bottle, and putting grass-fed butter and MCT oil into your coffee may be more fat that your body can handle, actually leading to the opposite effect than intended—inflammation. Even on a high-fat diet, too much dietary fat can—and often will—stall fat loss. Dial down that excess dietary fat and include more fiber-rich vegetables, berries, legumes, and non-gluten grains for a healthier, more diverse gut microbiome to keep your weight within a healthy range.

2. You can fit plenty of nutrient-dense carbs into your keto plan.

I’ve never had a patient who ate so much broccoli she got knocked out of ketosis. Once you’re getting sufficient dietary fat, you can incorporate tons of leafy and cruciferous vegetables, low-sugar fruit like berries and avocado, and even some starches like quinoa into your ketogenic plan. Your mileage may vary, of course, but even focusing on low-sugar vegetables will add an array of key nutrients to your meals.

3. Skip the processed stuff.

Ketogenic diets often fall into the same processed-food trap as Atkins. Today you’ll find keto bread, cookies, and pasta. You’ll find exogenous ketone supplements that promise you can get into ketosis in 30 minutes. Don’t fall for the hype: Eating a whole foods diet high in quality fats but also nutrient-dense plant foods creates the best avenue to get you into ketosis and promote health.

4. Be cautious about food sensitivities.

As the Atkins diet makes abundantly clear, problem foods like gluten and dairy can slip into the strictest low-carb or keto plans. I often see patients "doing keto" with massive amounts of cheese or processed meats full of fillers, which is a terrible idea. These potential top food sensitivities increase inflammation and create problems with gut permeability, leading to leaky gut syndrome.

7. Stop glorifying keto as some sort of magical state.

Being in ketosis can help you feel more alert, avoid sugar crashes that steal your energy, and possibly let you reach your goal weight. I say possibly because it doesn’t work for everyone. If you’re eating too many inflammatory calories you won’t lose weight, and furthermore, some people get bored with the lack of variety on keto diets. That’s where eating more complex carbs can rescue the plan. Try cyclical ketosis.

8. Be flexible. Get cyclical.

Cyclical ketosis means you’re sometimes in ketosis and sometimes aren’t. A few days each week—the night before workout days to build glycogen stores in your muscles—try increasing your intake of berries, higher complex carb veggies (like sweet potatoes), and non-gluten grains. It might knock you out of ketosis temporarily, but it also provides a wealth of nutrients to keep you lean, healthy, and happy. This is also called flexible ketosis, which creates metabolic flexibility—the holy grail of metabolism management. I’ve also talked about cycling ketosis with intermittent fasting, which provides a win-win strategy to reach your health goals.

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